Reduction and Reversion in the North American 
Salicales . 1 
BY 
RUTH HOLDEN, 
Wilby Prize Student of Radcliffe College. 
With Plates XX and XXI. 
I N the accepted classification of the Angiosperms, as presented by Engler 
and Prantl in ‘ Die naturlichen Pflanzenfamilien the Salicales are 
placed as the third alliance under the Archichlamydeae, the families below 
them being the Casuarinales and Piperales. A few families above them are 
the Juglandales and Fagales, with which the Salicales were formerly united 
to constitute the Amentiferae. The sequence of these orders is based on the 
development of the perianth and the character of the floral members. On 
this criterion the Salicales are certainly low in the series, having catkins of 
flowers which are naked in the axils of bracts. Even on floral structure there 
is one objection, however, to relegating them to this primitive group, viz. the 
nectaries of Salix . Insect pollination is generally conceded to be charac- 
teristic of the higher orders, yet the entomophilous Salix is placed below 
the anemophilous Juglandales and Fagales. Another objection to the 
existing classification is the fact that the Salicales are porogamous, while 
the Casuarinales below, the Juglandales and some of the Fagales above, are 
chalazogamous. Although there is some difference of opinion as to the 
relative primitiveness of porogamy and chalazogamy, it is a significant fact 
that chalazogamy is confined to lower families of the Archichlamydeae, 
while all the higher Dicotyledons and all the Monocotyledons are poro- 
gamous. Further, the step from the gy mnospermous condition, where the 
pollen-grains fall on the ovule and burrow through the intervening cells to 
the archegonia, to chalazogamy is short, but from the gymnospermous 
condition to porogamy is obviously great. 
Granting that insect pollination and porogamy are points against the 
primitiveness of the Salicales, geological evidence has been cited to prove 
their antiquity . 2 From the Potomac of Virginia, however, the lowest of the 
1 Contributions from the Phanerogamic Laboratories of Harvard University, No. 44, 
2 Penhallow, D. P. : A Systematic Study of the Salicaceae. American Naturalist, vol. xxxix, 
No. 464, Aug. 1905, p. 525. 
[Annals of Botany, Vol. XXVI. No. CL January, 1912.] 
